In August the U.S. Federal Reserve asked a number of big U.S. banks to undergo various "stress tests" in order to judge how their balance sheets could fare in worst-case financial scenarios.

The goal, as reported by CNBC, seems to be to assure that these companies can produce emergency capital given the sudden need.

U.S. banks interviewed by the Fed include Bank of America, JPMorgan Chase, Citigroup, and Morgan Stanley, according to CNBC's sources.

These interviews are a reaction to market volatility and the "too-big-to-fail" mentality.

"The summertime tests were a follow-up to a larger round of balance-sheet assessments that the country's 19 biggest banks undertook as part of the Comprehensive Capital Analysis and Review process that the Fed mandated in March, according to someone familiar with the matter."

Although the specific stress-stress scenarios are unknown, Bank of America "suggested to the Fed that it might introduce a Merrill Lynch tracking stock, among other things, say people familiar with BofA's proposal."

So we're wondering -- which U.S. banks offer relative safety for investors looking to gain exposure to the banking industry?

For ideas we looked toward the trades of banking insiders. If they're using their own cash to buy into the shares of their employers, you better pay close attention.

Do you agree with these bullish insiders? Use this list as a starting point for your own analysis. (Click here to access free, interactive tools to analyze these ideas.)

1. Capitol Federal Financial (Nasdaq: CFFN): Operates as the holding company for Capitol Federal Savings Bank that provides various banking products and services in Kansas. Over the last six months, insiders were net buyers of 139,500 shares, which represents about 0.09% of the company's 157.42M share float.

2. Capstead Mortgage (NYSE: CMO): Operates as a self-managed real estate investment trust in Dallas, Texas. Over the last six months, insiders were net buyers of 28,500 shares, which represents about 0.03% of the company's 83.23M share float.

3. Flagstar Bancorp (NYSE: FBC): Operates as the holding company for Flagstar Bank, FSB that offers consumer and commercial financial products and services to individuals, and small and middle market businesses in Michigan, Indiana, and Georgia. Over the last six months, insiders were net buyers of 72,793,301 shares, which represents about 37.29% of the company's 195.23M share float.

4. Sterling Financial (Nasdaq: STSA): Operates as the bank holding company for Sterling Savings Bank that provides various banking products and services to individuals, small businesses, commercial organizations, and corporations in the United States. Over the last six months, insiders were net buyers of 840,934 shares, which represents about 5.9% of the company's 14.25M share float.

List compiled by Eben Esterhuizen, CFA.

Interactive Chart: Press Play to compare changes in analyst ratings over the last two years for the stocks mentioned above. Analyst ratings sourced from Zacks Investment Research.

Disclosure: Kapitall's Becca Lipman and Eben Esterhuizen does not own any of the shares mentioned above. Insider data sourced from Fidelity, all other data from Finviz.

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